/* 
 * [New BSD License (BSD 3-Clause License)]
 * Copyright (c) 2012, Max Bechtold
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 *     - Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     - Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     - Neither the name of the Rel2Xml Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package maxbe.rel2xml.generator.docs.constraints;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Random;

import maxbe.rel2xml.generator.Table;
import maxbe.rel2xml.generator.docs.DataType;

/**
 * Generates unique numbers starting from startFrom (1 by default) and up to the
 * number communicated using methods mark or announce, if global is true.<br/>
 * One can specify a table in the dependency hierarchy for whose tuples the
 * values are to be unique. This holds under the restriction that this context
 * table can be reached by following the primary dependency on each level. If no
 * context is specified, but the respective table has dependencies, the context
 * will be set to the primary dependency of that table.
 * 
 * @author Max Bechtold
 * 
 */
public class UniqueNumbers implements ValueConstructor {

	/** Defines the table for whose tuples the generated values are unique */
	private final Table uniqueContext;

	/** Defines the starting point for unique, not random values */
	private final int startFrom;

	/** Determines whether the generated values are ascending or random */
	private final boolean random;

	/** If true, no value will be returned more than once */
	private final boolean global;

	/** Represents next value to be returned */
	private int nextValue;

	private static long seed = 876643092;
	private final Random rand;
	private List<Integer> numbers;
	private Iterator<Integer> iterator;

	private static final List<DataType> types;

	static {
		types = new ArrayList<DataType>();
		types.add(DataType.INTEGER);
	}

	public UniqueNumbers(boolean random, boolean global, int startFrom,
			Table uniqueContext) {
		this.random = random;
		this.global = global;
		this.startFrom = startFrom;

		this.uniqueContext = uniqueContext;

		this.nextValue = startFrom;
		rand = new Random(seed++);
	}

	public boolean isGlobal() {
		return global;
	}

	public Table getUniqueContext() {
		return uniqueContext;
	}

	@Override
	public boolean lengthVaries() {
		return false;
	}

	@Override
	public int getLength() {
		return -1;
	}

	@Override
	public int getSubLength() {
		return -1;
	}

	@Override
	public boolean needsAnnounce() {
		return isGlobal();
	}

	@Override
	public void announce(int number) {
		if (isGlobal() && random) {
			prepareNumbers(number);
		}
	}

	@Override
	public void mark(int number) {
		if (!isGlobal()) {
			if (!random) {
				nextValue = startFrom;
			} else {
				prepareNumbers(number);
			}
		}
	}

	@Override
	public String next() {
		if (random) {
			return iterator.next().toString();
		} else {
			return String.valueOf(nextValue++);
		}
	}

	@Override
	public List<String> next(int number) {
		List<String> result = new ArrayList<String>();

		if (random) {
			for (int i = 0; i < number; i++) {
				result.add(iterator.next().toString());
			}
		} else {
			for (int i = 0; i < number; i++) {
				result.add(String.valueOf(nextValue++));
			}
		}

		return result;
	}

	private void prepareNumbers(int number) {
		// Spare list generation if number of requested values doesn't change
		if (numbers == null || number != numbers.size()) {
			numbers = new ArrayList<Integer>();
			for (int i = startFrom; i < number + startFrom; i++) {
				numbers.add(new Integer(i));
			}
		}

		Collections.shuffle(numbers, rand);
		iterator = numbers.iterator();
	}

	@Override
	public String toString() {
		return (isGlobal() ? "global " : "")
				+ (random ? "random " : "")
				+ "unique number "
				+ (startFrom > 1 ? "starting from " + startFrom + " " : "")
				+ (uniqueContext != null ? "per " + uniqueContext.getName()
						: "");
	}

	@Override
	public List<DataType> getSupportedDataTypes() {
		return types;
	}
}
